Arthritis is much more common than you think, study suggests

Arthritis may affect about 91.2 million Americans—a figure nearly 70% higher than prior estimates, according to a study published in Arthritis & Rheumatology.

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Study details

For the study, S. Reza Jafarzadeh from the Boston University School of Medicine and David Felson from the University of Manchester and the Central Manchester NHS Foundation Trust in the United Kingdom reassessed current estimates on arthritis prevalence in the United States.

According to the researchers, CDC currently estimates that 22.7% of adults in the United States, or 54.4 million people, suffer from arthritis. However, the researchers pointed out that the estimate is based on the answer to one question on the 2015 National Health Information Survey (NHIS), which asks respondents if they have ever received an arthritis diagnosis from their physician.

They noted that prior research demonstrates a low sensitivity for arthritis surveillance based solely upon diagnoses from physicians. Specifically, the researchers cited a 2005 validation study that clinically verified responses to survey questions about arthritis among 389 health plan enrollees and found that roughly 47% of arthritis cases among people ages 45-64 and 31% of cases among people ages 65 or older were missed.

In response, the researchers reassessed the 2015 survey findings by using a more expansive definition of arthritis that adjusted for errors in CDC's more limited definition of arthritis and included self-reported symptoms. Specifically, the new definition, which is consistent with the National Arthritis Data Workgroup's definition of arthritis, considered respondents as presenting with the condition if they had either:  

  • Been diagnosed by a physician with the condition; or
  • Experienced joint-related pain, aches, or stiffness, other than in the back or the neck, within the past 30 days and initially felt the symptoms more than three months' prior.

Key findings

Using the new definition, the researchers found that of the 33,672 survey respondents:

  • 15.7% of men and 13.5% of women over the age of 65 reported having arthritis symptoms without having been diagnosed with the condition by a physician; and
  • 19.3% of men and 16.7% of women ages 18 to 64 similarly reported symptoms without a diagnosis.

Overall, based on the adjusted definition, the researchers estimated that 29.9% of men ages 18 to 64 had arthritis, as did 31.2% of women in that age group. Among individuals ages 65 years and older, the researchers estimated that 55.8% of men and 68.7% of women had the condition. Overall, the findings indicate that 91.2 million adults in the United States suffered from arthritis—an estimate that is 68% higher than CDC's current estimates. And of those, 61.1 million were between the ages of 18 and 64.

Discussion

The researchers said that relying on earlier measures of arthritis prevalence poses concerns not only because of the measurement errors, but because "implicit in the question on (physician)-diagnosed arthritis, when the response is positive, is that the surveyed individual sought or had access to medical care from a health professional." They explained, "However, a negative response to the (physician)-diagnosed question could be the result of either lack of medical attention to joint symptoms or a truly negative diagnosis with regard to arthritis." They added that a person who has been diagnosed with arthritis "may never be explicitly informed of the diagnosis."

In an accompanying editorial, Jeffrey Katz from the Orthopaedic and Arthritis Center for Outcomes Research at Brigham and Women's Hospital in Boston praised the study, writing that it "moves our field a large step forward, both by introducing a set of techniques that permits more nuanced use of existing survey data and by highlighting the limits of the specific questions deployed at present in national prevalence surveys."

That said, Katz cautioned that the new findings relied on the 2005 validation study, which had a limited sample size. "The estimated sensitivities and specificities of each survey item have limited precision," he wrote, calling for further research to "refine" the latest findings.

Regardless, Katz concluded that the findings "are sufficiently robust and concerning to justify a policy agenda encouraging greater investment of scarce resources into the pathogenesis, prevention and treatment of arthritis conditions" (Phillips, Medscape, 12/4; George, MedPage Today, 12/3).

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